csl: Add Gitter badges and fix HipChat template and skip flaky tests

There are (still) plenty of problems with our Github repos:

a) Finagle build is broken;
b) READMEs don't have a link to Gitter room;

Solution

a) Add `SKIP_FLAKY` env variable to Travis' config to skip all the
   flakey tests;
b) Add Gitter badge for all the projects (except for Ostrich) that
   redirects to Finagle's room;

RB_ID=761629

.travis.yml

@@ -24,8 +24,6 @@ notifications:
   hipchat: 
     rooms: 
       secure: tcb+hO7CxqN2n8w38cejS4j7a30clWbwMCBxSsPBK4XyqCInCrw5RT+KPRwd+UtoNREgPmk7QeaeGTonEgW8g/1ArK2RTHTFsmMskAnIVjanTlVl3BKBl9gmHeU+nSeBp+yQb808/JkUq174M3hyoYAtHh7gEJ0eUpmry3JjuQg=
-  template:
-    - '%{repository}: %{message} /cc @csl'
 
 before_script:
   # default $SBT_OPTS is irrelevant to sbt lancher